Path: utzoo!utgpu!news-server.csri.toronto.edu!cs.utexas.edu!wuarchive!rex!wpg!russ
From: russ@wpg.com (Russell Lawrence)
Newsgroups: comp.sys.sequent
Subject: Re: Dial-in/Dial-out on same tty port
Message-ID: <3602@wpg.com>
Date: 25 Jan 91 01:58:18 GMT
References: <1991Jan22.032421.9098@irscscm.UUCP> <31108@sequoia.execu.com>
Organization: WP Group, Metairie, LA
Lines: 46

In article <1991Jan22.032421.9098@irscscm.UUCP> mfaurot@bogart.UUCP (Michael Faurot) writes:
> I've got a Balance running Dynix 3.14 and would like to know if there's
> a program or means by which one can get both dial-in and dial-out
> useage of a tty port?  Please, no comments about upgrading to a
> Symmetry!  

In article <31108@sequoia.execu.com>, keith@sequoia.execu.com (Keith Pyle) writes:
> Don't bother with the Symmetry upgrade (is this comment about an upgrade
> acceptable? :-).  We have an S81 running 3.0.17 and Sequent still doesn't
> provide for this.  At least if they do, they refuse to tell us about it.
> 
> We've tried to get this BUG fixed for some time and have had no success
> with Sequent.  I guess they would rather sell more ports and have us buy
> more modems.

One of my customers has purchased a Gpx 6070 from Basic Four which will
be arriving in a few weeks, so I anticipate having to deal with the 
dialin/dialout problem sooner or later.  

Do the fopen() and fcntl() calls under dynix permit you to set and
clear the O_NDLAY flag?

If so, you could use one of the PD versions of uugetty to handle 
incoming calls without preventing folks from using the same 
line as a dialout port.  The uugetty would open the port with 
O_NDLAY clear, thus causing the open() to hang until CD 
goes high on the modem.  When that happens, the uugetty checks 
for the existence of a lock file in usr/spool/locks (or whereever 
locks are maintained under dynix).  If it finds a lockfile, it 
checks the process identified by the PID number in the lockfile 
to see if the process that created the lockfile is still active.  
If not, it "knows" that someone else is using the line for 
dialout.  In this event, the uugetty goes to sleep for periodic 
intervals until the process is no longer active.  If there isn't 
a lockfile, or the PID in the lockfile points to a dead process, 
uugetty behaves like a normal 'getty' program... setting the line
discipline, fetching the user's name, and subsequently exec-ing
'login'.

The potential problem (???) is that open() under dynix may not
hang under certain circumstances.  If so, you could still work
around the problem, but the solution might be messy.

-- 
Russell Lawrence, WP Group, New Orleans (504) 443-5000
russ@wpg.com   uunet!wpg!russ